Ball lamp



FIG. 1 is a perspective view of a ball lamp showing my new design;

FIG. 2 is a front view of the ball lamp shown in FIG. 1; and,

FIG. 3 is a top view of the ball lamp shown in FIG. 1.

The broken line disclosure represents a portion of the lamp which forms no part of the claimed design. 

CLAIM The ornamental design for a ball lamp, as shown and described. 